gecko-dev/gfx/layers/wr/StackingContextHelper.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef GFX_STACKINGCONTEXTHELPER_H
#define GFX_STACKINGCONTEXTHELPER_H
#include "mozilla/Attributes.h"
#include "mozilla/gfx/MatrixFwd.h"
#include "mozilla/webrender/WebRenderAPI.h"
#include "mozilla/webrender/WebRenderTypes.h"
#include "Units.h"
namespace mozilla {
namespace layers {
class WebRenderLayer;
/**
* This is a helper class that pushes/pops a stacking context, and manages
* some of the coordinate space transformations needed.
*/
class MOZ_RAII StackingContextHelper
{
public:
// Pushes a stacking context onto the provided DisplayListBuilder. It uses
// the transform if provided, otherwise takes the transform from the layer.
// It also takes the mix-blend-mode and bounds from the layer, and uses 1.0
// for the opacity.
StackingContextHelper(const StackingContextHelper& aParentSC,
wr::DisplayListBuilder& aBuilder,
WebRenderLayer* aLayer,
const Maybe<gfx::Matrix4x4>& aTransform = Nothing(),
const nsTArray<wr::WrFilterOp>& aFilters = nsTArray<wr::WrFilterOp>());
// Alternate constructor which invokes the version of PushStackingContext
// for animations.
StackingContextHelper(const StackingContextHelper& aParentSC,
wr::DisplayListBuilder& aBuilder,
WebRenderLayer* aLayer,
uint64_t aAnimationsId,
float* aOpacityPtr,
gfx::Matrix4x4* aTransformPtr,
const nsTArray<wr::WrFilterOp>& aFilters = nsTArray<wr::WrFilterOp>());
// The constructor for layers-free mode.
StackingContextHelper(const StackingContextHelper& aParentSC,
wr::DisplayListBuilder& aBuilder,
LayerRect aBoundForSC,
LayerPoint aOrigin,
uint64_t aAnimationsId,
float* aOpacityPtr,
gfx::Matrix4x4* aTransformPtr,
const nsTArray<wr::WrFilterOp>& aFilters = nsTArray<wr::WrFilterOp>());
// This version of the constructor should only be used at the root level
// of the tree, so that we have a StackingContextHelper to pass down into
// the RenderLayer traversal, but don't actually want it to push a stacking
// context on the display list builder.
StackingContextHelper();
// Pops the stacking context, if one was pushed during the constructor.
~StackingContextHelper();
// When this StackingContextHelper is in scope, this function can be used
// to convert a rect from the layer system's coordinate space to a LayoutRect
// that is relative to the stacking context. This is useful because most
// things that are pushed inside the stacking context need to be relative
// to the stacking context.
// We allow passing in a LayoutDeviceRect for convenience because in a lot of
// cases with WebRender display item generate the layout device space is the
// same as the layer space. (TODO: try to make this more explicit somehow).
wr::LayoutRect ToRelativeLayoutRect(const LayerRect& aRect) const;
wr::LayoutRect ToRelativeLayoutRect(const LayoutDeviceRect& aRect) const;
// Same but for points
wr::LayoutPoint ToRelativeLayoutPoint(const LayerPoint& aPoint) const;
// Same but rounds the rectangle to ints after transforming.
wr::LayoutRect ToRelativeLayoutRectRounded(const LayoutDeviceRect& aRect) const;
private:
wr::DisplayListBuilder* mBuilder;
LayerPoint mOrigin;
gfx::Matrix4x4 mTransform;
};
} // namespace layers
} // namespace mozilla
#endif /* GFX_STACKINGCONTEXTHELPER_H */